Estrogens are important physiological regulators of prolactin synthesis by the pituitary. Prolonged treatment with estrogens leads to the induction of pituitary tumors. We propose to investigate the molecular mechanisms involved in the regulation of prolactin synthesis. Primary emphasis will be focused on prolactin messenger RNA. Prolactin messenger RNA will be isolated and characterized. Purified messenger RNA will be used as a template for the synthesis of a copy of DNA which will be used as a hybridization probe for quantification of messenger RNA concentrations. The time course of estrogen effects on prolactin secretion, synthesis and messenger RNA levels will be determined. Cell free transcription studies will be used to examine the possibility of estrogen effects on prolactin messenger RNA synthesis. The ultimate goal of this research is to understand how estrogens regulate the expression of the gene for an important, biologically active hormone, prolactin.